BEIJING—China unveiled a litany of bribery and misconduct allegations against GlaxoSmithKline PLC, a move that industry experts said could presage a broader crackdown in a lucrative market for pharmaceutical and medical companies.

At a news conference on Monday, officials within the Ministry of Public Security's economic crime investigation unit said four high-level Chinese Glaxo executives have been detained over allegations that they "severely violated" Chinese law. The officials accused Glaxo staffers of using...